1. Field of the Invention
The present invention relates generally to a light transmission system for use in vehicle lighting systems, specifically a high efficiency illuminator for use with a light source.
2. Description of the Related Art
Conventional vehicle lighting systems typically utilize a bulb and reflector combination. In a bulb and reflector combination, a filament of the bulb is placed at or near a focal point of the reflector. The focal point of a reflector is that point at which parallel rays of light meet after being reflected by a reflective surface. Conversely, light rays emanating from the focal point are reflected as parallel rays of light. Energy supplied to the filament radiates as light over a 4.pi. steradian angle. A portion of the radiated light is collected by the reflector and reflected outward. The outwardly reflected light combines with light radiating outward directly from the filament to form a light beam. A lens is used to shape the light beam into a specified pattern as established by vehicle lighting standards.
Bulb and reflector combination have several disadvantages, including aerodynamic and aesthetic styling, e.g., the depth of the reflector along its focal axis and the dimensions of the reflector in directions perpendicular to the focal axis have greatly limited attempts at streamlining the vehicle. The heat generated during bulb operation must be dissipated and thus becomes a factor to consider when designing a vehicle lighting system. Also, bulbs burnout and must be replaced. Placing a bulb in a difficult to reach position creates maintenance problems and reduces design freedoms.
With the advent of light guides such as fiber optics, the ability to use a remote light source and a light guide to transfer light generated at a remote light source to a distant location became available. Other light sources such as a light emitting diode (LED) have also been used to replace a standard filament bulb. Light emitting diodes are used because they are less costly and emit a greater amount of light than typical filament bulb systems.
A lighting system showing or utilizing a LED is disclosed in U.S. Pat. No. 5,001,609. This patent discloses an LED illumination lamp producing a bright output over a pre-selected viewing angle having two focusing stages for concentrating the light emitted by the diode into a final desired viewing angle. A substantial portion of the usable light is light rays emanating directly from the light source. The device reflects only a certain portion of the light emanating from the diode, which limits the ability of the device to confine the light into the required photometric zones.
While this approach may have some limited use, it is desired to have an illuminator which collects and distributes substantially all of the light emanating from a light source thereby minimizing the number of light sources, LEDs or light guides necessary to develop the required lumens. Additionally, confining the light output exclusively to the required photometric zones maximizes illuminator efficiency and results in an optimum illuminator in terms of size and efficiency.